1. Field of the Invention
The present invention relates to an illumination lens.
2. Description of Related Art
JP 2004-356512 A, U.S. Pat. No. 7,934,858 B, and JP 4-36588 B for example propose illumination lenses for making an illuminance uniform in an illuminated surface of light radiated from LED (Light Emitting Diode) light source.
However, a conventional illumination lens is configured to provide a desired illuminance distribution when a light source is arranged at a specific position with respect to the illumination lens. Therefore, when the light source is not arranged at a specific position with respect to the illumination lens, there is a problem that a desired illuminance distribution cannot be provided.
It is therefore an object of the present invention to provide an illumination lens which suppresses a change of an illuminance distribution following a change of an arrangement position of a light source with respect to the illumination lens.